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M. PUPIN AND E. H. ARMSTRONG. SELECTIVELY OPPOSING IMPEDANCE T0 RECEIVED ELECTRICAL OSCILLATIONS.. APPLICATION FILED FEB. I0, 191.6.- RENEWED NOV. 6.1920.

1,415,845. Patented May 9,1922.

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UNITED STATES PATIENT OFFICE.

MICHAEL I. PUPIN, OF NORFOLK, CONNECTICUT, AND EDWIN H. ARMSTRONG, OF

' YONKERS, NEW YORK.

'SELECTIVELY OPPOSING IMPEDANCE TO RECEIVED ELECTRICAL OSCILLATIONS.

Specification of Letters Patent.

Patented May 9, 1922.

Application filed February 10, 1916, Serial No. 77,437. Renewed November 6, 1920. Serial No. 422,365.

To all whom it may concern:

Be it known that we, MICHAEL I. Form, a citizen of the United States, residing at. Norfolk, county of Litchfield, State of Connecticut, and EDWIN II. ARMSTRONG, a citizen-of the United States, residing at Yon kers, county of Westchester, State of New York, have invented certain new and useful Improvements in Selectively Opposing Impedance to Received Electrical Oscillations;

and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same. I This invention relates to an improvement in transmission of electrical. signals which consists in prolonging the time necessary for anelectrical action impressed upon the receiving conductor to arrive at a local receiving conductor'is not instantaneous and therefore the local power source will not be excited to aid an electrical action of a duration shorter than a fixed minimum time interval.

For the purpose of illustrating the manner in which this invention is carried out in practice, reference is made now to the diagrammatic drawing which forms a part of this specification.

. This diagram represents an antenna of a radio-receiving system in whicha high resistance is inserted for the purpose of dissipating the energy. of the incoming waves and which is provided with a source of power which, at the signalling frequency, will compensate these losses. In the arrangement shown this high resistance 1s 1nserted in the form of distributed resistance along the length of the antenna 1, as indicated by 1?, and the additional concentrated resistance 2 near the lower end of the antenna. The method of compensation employed is not in itself any part of the present invention, but it is illustrated and described here for the sake of. completing the disclosure. The method consists, broadly speaking, in providing .a local source of energy, together with means, responsive to received, waves of a predetermined frequency, for impressing this local energy upon the receiving conductor to compensate, for'that particular frequency, the energy losses incident to the high resistance of theconductor. The means employed consist of an electric valve, in this case, an audion, upon the grid of which the received oscillations are impressed thereby releasing energy from the local battery in the output circuit of the audion. This energy is transferred through the transformer 7 and the circuits associated therewith, including the coil 11 and the companion coil 3, into the antenna, a second electric valve 8 being arranged in cascade with the valve 6, if desired, to increase the negative resistance re action, of the compensator. This compensating arrangement is already known. The additional element introduced into the receiving system described here is a wave conductor system-the well known artificial line denoted by 5 and consisting of a suitable number of preferably equal inductances 12, 13, 14., .and equal condensers 15, 16, 17, c When an electrical pulse is impressed upon the antenna it is communicated, as is well known, to the exciting circuit of the resistance compensator 6, 7, 8, through the mutual inductance. 4, 22. This action will be transmitted from 22 to the local energizing circuit over the artificial line and its time oftransmission is determined by the total inductance, capacity and resistance of the line. Let L, C, and R be the total inductance, capacity and resistance of the artificial line, then the time of transmission 6 will be approximately t =10* 0, seconds L 6 X 10 henrys C 12 X 10- microfarads t, 8.4 X 10 seconds.

Let

sists of six equal sections; and oscillations of this frequency will not be assisted by a resistance compensator selective to a signalli-n' frequency of 25000 P. P. S.

l f the signalling frequency is 25000 P. P. Si thewartificial line will develop approximately two wave lengths for this frequencyand, therefore, there will be a shift in phase of 720 degrees between the steady signalling waves and the energy introduced by the energizing circuit of the resistance compensator through the inductance 3-11 into the receiving antenna. Thisshift in phase cannot and does not, obviously, produce any detrimental effect upon the etli-' ciency of interchange of energy between the energizing circuit and the antenna in response to the excitation of the steady signal-- ling waves, and, therefore, the negative resistance produced in the antenna by the local power source is independent of this phase relation, so long as the signalling wave is simple harmonic or departs from the simple harmonic form slowly. v

The phase relation between the action of the" signalling waves and the reaction of the resistance compensator may be adjusted in well known ways as by varying the inductance of the artificial line or the tuning elements ofthe compensator. Thesetuning elements include, as is well known, the condensers and inductances in the grid and plate circuits of the electric valves 6 and 8.

For therpu to associate with one of the circuits of the re ceiving system, and preferably with the output circuit of the lastvalve, a suitable detector circuit. We have here illustrated a coil 20 associated with'the coil 11 and connected in series with a rectifying detector 21 and a telephone 19, but it will be understood shorterduratl'on than the signal.

What we claim is: 1. A receiving conductor in energy-transose of detecting the received s1gnal's,it is on y necessary, as is well known,

ferring relation to the energizing circuit of a resistance compensator e ective upon the receiving conductor, and a wave conductor system connecting the receiving conductor to the exciting circuit of the resistance compensator and having a predetermined inductance, capacity and resistance affording a substantial time interval of energy transmission over the Wave conductor, whereby the positive resistance of the receiving conductor is opposed to received electrical disturbancesof short duration but is compensated for received harmonic impulses of longer duration.

'2. A receiving conductor in energy-transferring relation to the energizin circuit of a resistance compensator eective upon the receiving conductor, and a wave conductor system connecting the receiving conductor to the exciting circuit of the resistance compensator and having inductance capacity and resistance affording a substantia time intervalof energy transmission over the wave conductor and attuned to'electrical impulses of predetermined frequency, whereby the positive resistance of the receiving conductor is opposed to received electrical disturbances of short duration but is compensated for received harmonic impulses of longer duration and of the predetermined frequency.

3. A receiving conductor offeringhigh inenergy from the local source'to the receiving conductor, after the a plicationof waves of that frequency'throug 1 a predetermined time interval to compensate the energy lossesin the receiving conductor for waves of that frequency.

5. A receiving conductor ofi'erin high initial resistance to receivedv electrical wave.

duced by the local power source after a fixed for aiding the effect of the electric Waves by time interval. the reaction produced by the local source 7. In a Wave signalling system, means for after an interval of time. exciting a local power source by the action In testimony whereof We aflix our signaof the electric Waves to produce a reaction tures.

MICHAEL I. PUPIN.

comprising an electric valve, means for increasing the effect of the reaction, and means EDWIN H. ARMSTRONG. 

